Symptoms affect the ear, temporal lobe, leaf blade, and leaf sheath. The discovery of the disease in China is mainly responsible for Kyrgyzstan 63 inbred lines. The ear infections were infested downward from the tip of the ear, and the grain of the ear was coal-smeared. The black mold layer on the surface of the grain and between the grains was the conidial stem and conidia of the pathogenic bacteria. The diseased granules were dry and rot, and the seeds were pulverized by hand. The temporal lobe lesions are not plastic lesions. Some of them are dark brown and generally do not form black moldy layer. The pathogens extend from the loquat leaves to the inside of the ear and damage the kernels and cobs. The leaves were infected with primary water-soaked light green to yellow spots, scattered and then expanded into round to oval round lenticular spots. The center of the lesion is light brown with brown edges, and the periphery has a yellow-green halo, with a size of 5-153-5 (mm). Occurrences of long linear spots are sometimes observed, and black mold layer is also formed on the lesion surface. When the leaf sheath is infected, it begins with a nascent brown spot and then expands into an irregularly shaped large spot. It also has a concentric ring pattern and produces a layer of black mold on the surface. Infected inbred line 478 of the ear rot disease of the round spot disease, the length of black rot of the tip of the ear was 5.3-9.3 cm, accounting for 2/5-3/5 of the length of the ear, and the base of the ear was not infested. The symptoms on the ear of the inbred line of the Ji-63 were similar to those on the ear of the T-strain of the T-species of the T. brassicae, and attention should be paid to the difference. The disease has different symptoms in inbred lines 478 and Kyrgyzstan 63, and may be different reaction types. Distributed in Jilin, Liaoning, Hebei and other provinces.
The pathogen, Bipolaris carbonum Wilson, is called Charpy spp. Synonyms B. Zeicola (Stout.) Shoem., Helminthosporium carbonum (Ullstrup) Shoem. The sexual state is Cochliobolus carbonum Nelson. Conidiophore stalks dark brown, light apical, solitary or 2-6 clumps, erect or geniculate, blunt at both ends, basal cells swollen, with 3-5 septa, size 64.4-997. 3-9.9 (um). Conidia dark olive, long oval, central width, both ends narrow, thick spore wall, top cells and basal cells blunt, most upright, umbilical point is small, not obvious, with 5-10 membrane, More than 5-7, size 33-10512-17 (um). The bacteria has a small variety.
Transmission routes and conditions of the disease The route of transmission of the disease is similar to the size of the spot. Because of the heavy incidence of the ear, the pathogen can lurk over the winter in the ear. The disease-inducing effect of seeds carrying bacteria in the following year is very large, and some infected seeds cannot germinate and rot in the soil, causing seedling disease or dead. In addition, residues of diseased plants that have been left in the field or on straw stubble can also be the primary source of infestation in the following year. When the conditions are appropriate, the spores of the overwintering fungus spread to the corn plants and germinate and invade after 1-2 days of incubation. Conidia are also produced on the lesions, spread by wind and rain, causing leaf spots or ear rot and undergoing multiple infections. Corn silking to filling period is a critical period for the invasion of the disease.
Control methods (1) Selection of disease-resistant varieties The current breeds of inbred lines and hybrids with resistance to round spot disease are: Erhuang, Tidan 8, Ying 55, Liao 1311, Ji 69, Wu 105, Wu 206, Qi 3l , White, H84, 017, Kyrgyzstan l07, Chundan 34 and so on. (2) It is forbidden to plant seeds from the ward, and to completely treat the diseased body before the emergence of corn to reduce the initial infestation source. (3) In the high corn silking period, that is, when 50%-80% of the ears have been spun, spraying 25% triadimefon 500-600 times solution, 50% carbendazim, 70% mancozeb, to the ear. Wettable powder 400-500 times liquid, once every 7-10 days, continuous control 2 times. (3) Seedling varieties can also be seeded with 0.3% seed weight of 15% tris-pj WP prior to sowing. (4) For sensitive inbred lines or varieties, spray 25% tri-pj-ketone (triadimefon) wettable powder 1000 times or 40% Fuxing-starvest oil 8000 times in the tip period of the ear, control every 10-15 days. 2-3 times.